I. Field
The present methodology relates generally to communication, more specifically to techniques involved in limiting access to a shared resource, and still more specifically to limiting access to data used in determining the position of a wireless network component.
II. Background
In many systems, particularly communication networks, data and other resources are often requested by entities in communication with the network. Accessing such data can tax a communication network, circuitry, or other system hardware. In wireless communication networks, data is often requested and exchanged among entities operating in the network. One example where data is often requested is in a wireless communication network where the position of a mobile terminal operating within the network is desired and data from the network is beneficial in determining the position.
For example, an enhanced 911 (E911) wireless service promulgated by the Federal Communications Commission (FCC) requires the position of a terminal (for example, a cellular telephone) to be provided to a Public Safety Answering Point (PSAP) each time a 911 call is made from the terminal. In addition to the FCC mandate, various applications may use the position of a terminal to provide value-added features and possibly generate additional revenues.
In general, an estimate of the position of a wireless terminal, also commonly known as a mobile station (MS), user equipment (UE), cellular telephone, personal communication system (PCS), wireless laptop computer, etc., may be derived based on (1) the distances or ranges from the terminal to a sufficient number of transmitters, e.g., three or more transmitters, and (2) the known positions of these transmitters. Each transmitter may be a satellite or a base station in a wireless communication network. The distance to each transmitter and/or the position of each transmitter may be ascertained based on a signal sent by the transmitter.
Global Positioning Systems (GPS) determine position based on the measurement of the times of arrival at a GPS receiver antenna of the GPS signals broadcast from orbiting satellites. One disadvantage of the GPS system for location determination is the relatively long time needed to perform signal acquisition under certain conditions. Satellite signals cannot be tracked until they have first been located by searching in a two-dimensional search “space”, whose dimensions are code-phase delay and observed Doppler frequency shift.
In order to reduce this delay, information may be provided to aid a GPS receiver in acquiring a particular signal. Such assistance information permits a receiver to narrow the search space that must be searched in order to locate a signal, by providing bounds on the code and frequency dimensions. A system that employs a GPS receiver augmented with externally sourced GPS assistance data is commonly referred to as an “assisted global positioning system” (AGPS).
One example of an AGPS system is a wireless mobile station (MS) with GPS capabilities in communication with one or more base stations (BSs), also referred to as base transmitting stations (BTSs) or node Bs, which in turn communicate with one or more servers, also called Position Determination Entities (PDEs) or Serving Mobile Location Centers (SMLCs) depending upon the communication air interface protocol. The PDE derives GPS assistance information from one or more GPS reference receivers. The PDE also has access to a means of determining the approximate mobile station position. This might consist of a “base station almanac” (BSA) that provides BTS/node B location based upon serving cell identification (ID) reported by the mobile station. The PDE computes the assistance information customized for the approximate mobile station position. The PDE also maintains a GPS database that contains reference time, satellite orbit almanac and ephemeris information, ionosphere information, and satellite working condition (“health”) information.
Position location for a terminal can be determined at the terminal (sometimes referred to as MS-based positioning mode) with assistance from a PDE, for example, in an AGPS system, or at the PDE and transmitted back to the terminal using information acquired by the terminal (sometimes referred to as MS-assisted positioning mode).
During MS-based positioning mode, when a GPS engine requires updated aiding data such as ephemeris data, almanac data regarding the location of satellites or base stations, timing information for the base stations and/or satellites, or seed position (such as, but not limited to that determined by advanced forward link trilateration (AFLT)), and so on, the next position fix will result in the mobile station contacting the communication network for data.
While normal operation should limit such intermittent requests to between every thirty to ninety minutes, there is a possibility that due to a variety of connectivity problems, for example air interface issues, authentication or authorization problems, problems with the data network, problems with the PDE, etc., MS-based aiding data download requests may fail, resulting in aiding data being requested more frequently. As a result of the inability to download MS-based aiding data, frequent, repeated attempts are made by the mobile station to access the network to retrieve the aiding data, and these attempts result in continued failure. Such communication consumes additional power and communication system bandwidth that impacts overall capacity. A need exists to prevent a mobile station from repeatedly accessing the network for MS-based aiding data when network or other conditions cause frequent failed downloads.